Arylpyrrole carbonitrile compounds are highly effective insecticidal, acaricidal and nematocidal agents with a unique mode of action and a broad spectrum of activity. In particular, 2-aryl-5-(trifluoromethyl)pyrrole-3-carbonitrile compounds demonstrate effective control across a wide array of pests and can control resistant pests such as pyrethroid-, organophosphate-, cyclodiene-, organochlorine-, organotin-, carbamate-, and benzophenylurea-resistant biotypes of Helicoverpa/Heliothis spp., Spodoptera spp., Trichoplusia spp., Pseudoplusia spp. and Tetranychus spp.. Because there is no apparent cross-resistance, 2-aryl-5-trifluoromethylpyrrole-3-carbonitrile compounds and their derivatives have potential for use in resistance management programs. Further, said pyrroles have little effect on beneficial species making them excellent candidates for integrated pest management programs, as well. These programs are essential in today's crop production.
Therefore, methods to prepare said pyrroles and intermediates to facilitate their manufacture are of great value. Among the methods known to prepare 2-aryl-5-(trifluoromethyl)pyrrole-3-carbonitrile is the 1,3-dipolar cycloaddition of the mesoionic intermediate product of the acid catalyzed cyclization of a Reissert compound with a suitable alkyne to give an N-substituted pyrrole product as described by W. M. McEwen, et al, Journal of Organic Chemistry, 1980, 45, 1301-1308. Similarly, munchnones (which are also zwitterionic intermediates) undergo 1,3-dipolar cycloaddition to give N-substituted pyrroles. In addition, on a manufacturing scale, the 1,3-dipolar cycloaddition of 3-oxazolin-5-one with 2-chloroacrylonitrile is described in U.S. Pat. No. 5,030,735.
It is an object of this invention to provide an alternate source of important intermediate compounds and manufacturing routes to a new class of highly effective pesticidal compounds.
It is a feature of this invention that the process of manufacture provides a regiospecific product.
It is an advantage of this invention that the process of manufacture provides an N-unsubstituted pyrrole (NH-pyrrole) intermediate which is capable of further derivatization of the pyrrole ring nitrogen to give a wide variety of pesticidally active pyrrole products.